The present invention relates to an operating valve assembly with a pressure compensation valve.
When a pressurized fluid discharged from a single hydraulic pump is distributed to a plurality of actuators, it is typical to provide a plurality of operating valves in a discharge line of the hydraulic pump and to supply a pressurized fluid to respective actuators by switching operating valves. In such a hydraulic circuit, if the pressurized fluid is to be supplied to a plurality of hydraulic actuators simultaneously, the pressurized fluid may be supplied only to the actuator having a smaller load and cannot be supplied to the actuator having the greater load. As a solution for such a problem, there have been proposed hydraulic circuits, such as that disclosed in Japanese Examined Patent Publication (Kokoku) No. Heisei 2-49405.
FIG. 1 shows one example of the conventional hydraulic circuit. The shown hydraulic circuit includes a plurality of operating valves 2 in a discharge line 1a of a hydraulic pump. A pressure compensation valve 5 is provided in each circuit 4 connecting each operating valve to a hydraulic actuator 3. The highest pressure among the pressures in the respective circuits, i.e. among the load pressures, is detected by a load pressure detecting path 7 incorporating check valves 6. The detected highest load pressure acts on each of the pressure compensation valves 5 for setting a set pressure at a pressure level corresponding to the detecting load pressure. In conjunction therewith, an outlet side pressure of each operating valve is controlled to be lower than the set pressure so that when the operating valves 2 are operating simultaneously, the pressurized fluid may be distributed to respective actuators at a distribution ratio proportional to the open areas of the operating valves.
The hydraulic circuit of the type set forth above is complicated since it requires the operating valve 2, the pressure compensation valve 5, and the load pressure detecting path 7 in the circuit 4. Furthermore, such a hydraulic circuit is bulky and thus requires a wide space for installation. In order to solve this problem, it may be considered to provide the operating valve 2, the pressure compensation valve 5 and the load pressure detecting path 7 within a single block. However, if these components are simply aggregated within the single block, the block inherently becomes large and cannot be made compact.